The present invention relates to the general field of making gas turbine casings out of composite material, and more particularly fan retention casings for aeroengine gas turbines.
It is common practice for a fan retention casing to be constituted by a relatively thin wall that defines the passage for admitting air into the engine and that supports an abradable material in register with the path followed by the tips of the fan blades, that possibly also supports a sound treatment coating, and that supports a shield structure that is fastened to the outside of the wall over the fan in order to retain debris, such as items that have been ingested or fragments of damaged blades that are projected by centrifuging, for the purpose of preventing them from passing through the casing and reaching other portions of the aircraft.
Proposals already exist to make a fan retention casing out of composite material. By way of example, reference may be made to Document EP 1 961 923, which describes fabricating a casing out of composite material of varying thickness, which method comprises forming fiber reinforcement as superposed layers of a fiber texture and densifying the fiber reinforcement with a matrix. More precisely, that document provides for using a takeup mandrel for the three-dimensional weaving of the fiber texture, which texture is then wound as superposed layers on an impregnation mandrel of profile that corresponds to the profile of the casing to be fabricated. The preform as obtained in that way is held on the impregnation mandrel and it is impregnated with resin, which resin is then polymerized.
It should nevertheless be observed that during the winding operation, a portion of the preform (more precisely its bottom face) is not visible to operators who are situated on a work platform that is conventionally located above the winder machine. That configuration thus prevents various anomalies being detected that might affect the preform, such as pollution (adhesive tape, cut fibers, . . . ) or weaving faults in the portion of the preform that cannot be visually inspected by the operators. Unfortunately, this winding operation is the last step in the fabrication process where such anomalies can still be detected. Thus, if they are not identified during winding, they are hidden by being covered in the superposition of layers of the preform.
It is important to observe that these anomalies that are situated on the hidden face of the preform during the winding operation, are also not detectable during the prior weaving operation since they are likewise hidden while weaving on a loom, for example.
Consequently, there exists a need to have a winding machine or a weaving machine (or loom) that makes it possible to detect both pollution and weaving faults on the hidden face of the preform prior to any winding. After winding, it is impossible to inspect for such contamination and faults of the preform and it is then impossible to validate the winding operation.